I have a data frame:
> head(df)
Time Temp Conc Repl Log10
1 0 -20 H 1 6.406547
2 2 -20 H 1 5.738683
3 7 -20 H 1 5.796394
4 14 -20 H 1 4.413691
5 0 4 H 1 6.406547
7 7 4 H 1 5.705433
> str(df)
'data.frame': 177 obs. of 5 variables:
$ Time : Factor w/ 4 levels "0","2","7","14": 1 2 3 4 1 3 4 1 3 4 ...
$ Temp : Factor w/ 4 levels "-20","4","25",..: 1 1 1 1 2 2 2 3 3 3 ...
$ Conc : Factor w/ 3 levels "H","L","M": 1 1 1 1 1 1 1 1 1 1 ...
$ Repl : Factor w/ 5 levels "1","2","3","4",..: 1 1 1 1 1 1 1 1 1 1 ...
$ Log10: num 6.41 5.74 5.8 4.41 6.41 ...
> levels(df$Temp)
[1] "-20" "4" "25" "45"
> levels(df$Time)
[1] "0" "2" "7" "14"
As you can see, "Time" and "Temp" are currently factors, not numeric.
I would like to change these columns into numerical ones.
df$Time<- as.numeric(df$Time)
doesn't work, as it changes to the factor level indices (1,2,3,4)
instead of the values (0,2,7,14).
There must be a direct way of doing this in R.
I tried recode() in 'car':
> df$Temp<- recode(df$Temp, '1=-20;2=25;3=4;4=45',as.factor.result=FALSE)
> head(df)
Time Temp Conc Repl Freq
1 0 -20 H 1 6.406547
2 2 -20 H 1 5.738683
3 7 -20 H 1 5.796394
4 14 -20 H 1 4.413691
5 0 45 H 1 6.406547
7 7 45 H 1 5.705433
but note that the values for 'Temp' in rows 5 and 7 are 45 and not 4,
as expected, although the result is numeric. The same happens if I
use the order given by levels(df$Temp) instead of the sort order in
the recode() 2nd argument.
Any hints?
================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: r...@lcfltd.com
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
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